A spike in flu cases is straining Perth hospital emergency departments as the city suffers through its highest levels of influenza-like illnesses in four years.

The flu surge resulted in 160 hours of ambulance ramping across Perth's tertiary hospitals on Monday, with the number of people presenting to emergency departments having soared in the last fortnight.

WA Health said elderly people were being affected the most by the current strain, and a lack of Commonwealth-funded aged care beds was contributing to the pressure.

The department also said August was typically the busiest time of the year for hospital emergency departments.

Attendances across the metropolitan area this month are up by 97 people per day on July.

WA Health chief medical officer Professor Geelhoed said the influenza season had started relatively late, with a significant increase in flu-like illness over the past two weeks.

"Levels of influenza activity are currently the highest they have been since 2012," Professor Geelhoed said.

"In the past week alone, there has been a 10 per cent increase in the number of patients presenting with a flu-like illness compared to the same week last year."

He said hospital staff were also succumbing to the illness, placing more strain on the system.

The dominant influenza virus strain circulating this winter is known as A/H3N2.

WA Health said it disproportionately affected elderly people, who were more likely to require hospital admission.

"Unfortunately, WA has the lowest number of aged care beds per head of population in Australia, which means there are many elderly people in our hospitals waiting for beds to become available in residential care," Professor Geelhoed said.

Professor Geelhoed said anyone who did not require emergency care should consider other healthcare options such as a GP or Healthdirect Australia.

St John Ambulance chief executive Tony Ahern said August had been a bad month for ramping, but that the numbers of patients taken by ambulance to the ED that did not really need hospital help were very small.

"Our workload predominately is elderly," he said.

"We see a lot more elderly patients, so when these sorts of things are happening, that number goes up."